The value of a snack is $2-$4 and the value of a kids chacter meal is around $15 with tax and tip. You can skip every child CS meal and still come out ahead. There are some CS that offer decent kids meals. Some of the CS restaurants, particularly in the resorts, might give you a child portion of an adult item if you ask nicely and you can always use your childs CS meal for the drink and fries.
Disney has a dollar value associated with each item. The non-Disney restaurants are reimbursed a flat amount, regardless of what you order. The adult CS meal is $8-$9, I don't know what it is for a child CS meal. Remember the snack is the same for both adults and children. My guess is the snack is valued at around $2.
Disney is keeping the plan simple. They coud go to a straight credit system. 1 credit gets you a snack, 2 credits a kids CS meal, 4 credits an adult CS meal and so on. Having a way to up a kids meal to an adults meal, either with cash or extra credits, might benefit some guests.